The advent of portable computers has created demand for display devices which are lightweight, compact, and power efficient. Since the space available for the display of these devices precludes the use of a conventional cathode ray tube (CRT), there has been an effort to produce flat panel displays having comparable or even superior display characteristics.
Liquid crystal displays are commonly used for laptop and notebook computers. These displays may suffer from poor contrast, a limited range of viewing angles, and power requirements which are incompatible with extended battery operation. In addition, color liquid crystal displays tend to be far more costly than CRTs of equal screen size.
As a result of these limitations of liquid crystal display technology, field emission display technology has received more attention in the industry. Field emission flat panel displays employ a matrix-addressable array of field emission cathodes in combination with an anode comprising a luminescent screen. The manufacture of inexpensive, low-power, high-resolution, high-contrast, full-color flat panel displays using this technology appears promising.
In order for field emission displays to operate efficiently, it is desirable to maintain a vacuum within the cavity of the display, typically less than 10.sup.-6 Torr. The cavity is pumped out and degassed before assembly, but over time the pressure in the display builds up due to outgassing of the components inside the display and to the finite leak rate of the atmosphere into the cavity. Getters are employed as pumps that adsorb these undesirable gases in order to maintain a minimum pressure in the cavity.
In field emission flat panel displays, the cathode or emitter plate and the anode plate may be spaced from one another at a relatively small distance. This spacing, typically on the order of two hundred microns, limits the total volume of the cavity enclosed within the display screen. Due to the limited volume within the cavity, the getter is normally placed in peripheral regions, such as in the pump-out tubulation at the back of the display. The placement of the getter material outside of the active region of the display in combination with the small volume within the cavity severely reduces the pumping effectiveness of the getter.